There are fears that the debate will descend into the sort of squabbling and political brinkmanship that marked the last effort to raise the ceiling in the summer of 2011.

‘‘The pressure on the US rating, if anything, is increasing,’’ David Riley, managing director of Fitch Ratings’ global sovereigns division said at a London conference. ‘‘We thought the 2011 crisis was a one-off event . . . if we have a repeat we will place the US rating under review.’’

If that happens, Riley said there was ‘‘a material risk’’ of the rating coming down, which could mean the United States would face steeper costs when it comes to servicing its debt.

If Fitch does move to downgrade the United States, it will join Standard & Poor’s, which stripped the United States of its triple A rating for the first time in the country’s history.